Isomerization Processes Observed for Chromium Compounds by Using the Gas Chromatographic Reactor

Philip J. Marriott, Yee Hing Lai

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Abstract

Two volatile chromium compounds, tris(1,1,1-trifluoro-2,4-pentanedionato)chromium(III) [Cr(tfa)3] and (2-methylnaphthalene) tricarbonylchromium [2-MenaphCr(CO)3], have been studied gas chromatographically. The resolution of geometrical isomers of Cr(tfa)3 using gas chromatography at sufficiently high temperatures (150–200 °C) permitted the dynamic interconversion process of the isomers to be studied. The use of high-resolution capillary columns aided this study. The activation energy for cis trans isomerization was estimated to be ca. 130 ± 10 kJ mol-1, and the twist mechanism was believed to be operative. Successful gas chromatographic separation of isomers of a bicyclic polyene-M(CO)3 system is reported for the first time. The rearrangement of the -Cr(CO)3 group can be followed in the gas chromatographic reactor; however, direct on-column injection is necessary in order to overcome decomposition of the compound, and this makes extraction of thermodynamic data less straightforward. An intramolecular (nondissociative) mechanism for the rearrangement is supported, and activation energies for isomer interconversion were estimated at 94 ± 7 and 100 ± 10 kJ mol-1, respectively.

Original languageEnglish
Pages (from-to)3680-3683
Number of pages4
JournalInorganic Chemistry
Volume25
Issue number20
DOIs
Publication statusPublished - 1 Jan 1986
Externally publishedYes

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